This invention relates to the creation and harvesting of algal turf. Such turf may be grown under natural or artificial light in a regime utilizing repetitive water motion. Such turfs are known to be efficient scrubbers of carbon dioxide, nutrients and a variety of pollutants found in natural or waste water. As a result of the scrubbing action, such turfs may produce biomass and oxygen to a certain degree. They also raise the pH of the water, and under low nutrient conditions can be used to fix nitrogen.
Accordingly, algal turf scrubbing can potentially be used for a variety of applications. For example, the scrubbers can be used to replace the biological or bacteriological filters in aquaria. Scrubbers can also be used to remove nutrients and other contaminants from polluted waters. Finally, by harvesting the algal mass, the technique can be used to produce biomass as an energy source, as a fertilizer or as a human or an animal food supplement.
Studies in algal turf production are well known and reported in the literature. For more than 20 years, tropical reefs have been acknowledged to be among the most productive of natural systems. For example, in Lewis, "Processes of Organic Production on Coral Reefs", pp. 305-347, 52 Biol. Rev. (1977), production values as found, for example, on page 312 therein, indicate that coral reefs are among the highest producers in primary production values for pelagic, benthic and terrestrial ecosystems. Notwithstanding the values demonstrated in some earlier literature, recent efforts have demonstrated that those estimates of reef primary productivity were conservative. The mean reported value, 10.3 gC/m.sup.2 /day should be contrasted to values ranging from 19.2 to 32.7 gC/m.sup.2 /day in a 1980 study referring to St. Croix reefs. Such recent studies have demonstrated that algal turfs in conjunction with wave surge have been identified as the primary source of most reef productivity.
Within this technology it has been known that the removal or severe reduction of wave surge motion greatly reduces primary productivity as shown in FIG. 2, a typical daily cycle of oxygen concentration in a reef microcosm. Reef production is accurately measured only near saturation since atmospheric exchange is a factor at higher or lower oxygen concentrations. As shown by the dotted line trace 2 when a wave generator, used in such reef microcosm devices, is stopped, given the same current, light, and nutrient levels, net productivity is nearly zero. In FIG. 2, the lack of an oxygen spike when the wave generator is restarted indicates that greatly reduced production is a real factor as opposed to an apparent condition because storage has not occurred.
Additionally, within the reported literature on research in this technology, there are a number of reports dealing with algae techniques for waste recycling, oceanic farming, or the like. Contemporary research can be grouped in two distinct categories: those utilizing macro algae and those using planktonic algae. In the first group, macro algae reports dealing with waste recycling or the like can be found in Ryther, et al, "Physical Models of Integrated Waste-Recycling Marine Polyculture Systems", Aquaculture, 5, 163-177 (1975); California Institute of Technology, Graduate School, Project "Evaluating Oceanic Farming of Seaweeds As Sources of Organics and Energy", U.S. Department of Energy, Division of Solar Technology, Contract E (04-3)-1275; and Washington State Department of Natural Resources, Project "Aquaculture of Seaweeds on Artificial Substrates", U.S. Department of Commerce, Contract R/A-12. In the case of planktonic algae, Goldman et al, "Relative Growth of Different Species of Marine Algae in Wastewater-Seawater Mixtures", Marine Biology, 28, 17-25 (1974); Karolinska Institutet, "Investigation of an Integrated Aquatic System for Storing Solar Energy in Organic Material", Namnden for Energiproduktionforskning, No. 53 3065 062; and State of Hawaii Natural Energy Institute, "Energy from Algae of Bioconversion and Solid Waste", Hawaii State Government, demonstrate the status of contemporary research using that type of algae.
In either case, research to date has not utilized wave surge motion to enhance the exchange of metabolites between algal cells in the water medium. Also, these known research techniques have not recognized the cruciality of macro algae size, vis-a-vis the shading of one cell by another. Accordingly, such techniques are not suitable for optimum biomass production and the propensity of removing nutrients and other contaminants from polluted waters is severely limited.